Thread retainer for sewing machines

ABSTRACT

A double-lockstitch sewing machine, provided with a threadcutting mechanism, has a thread retainer for supplying a predetermined thread length of upper thread at the conclusion of a stitching operation and as a preliminary to a subsequent stitching operation. The retaining arrangement includes a thread brake which is released at the end of the stitching operation and an eye for drawing the released thread from a spool or other supply to provide the desired length.

llnited States Patent Nicolay 5] Feb. 8, 1972 [54] THREAD RETAINER FORSEWING 2,584,013 1/ 1952 Hagquist ..112/241 MACHINES 2,925,058 2/1960Conrad ....l12/254 2,976,831 3/1961 Hacklander.. ....112/254 X [721 Km WBmlefeli Germany 1,273,157 7/1918 De Voe ..112/241 [73] Ass1gnee:guarl'llsrloppwerh Gmbfl, Brelefeld, Ger- FOREGN PATENTS OR APPLICATIONS[22] Filed, July 1 1970 1,128,726 4/1962 Germany ..112/241 i [21]Appl.No.: 51,530 Primary Examiner-Jordan Franklin AssistantExaminer-George H. Krizmanich 301 Foreign Application Priority umAmmeyxal Rm July 3, 1969 Germany ..P 19 33 780.5 [57] ABSTRACT Adouble-lockstitch sewing machine, provided with a thread- ..ll2/2:6!1bi/92/5X2) cutting mechanism has a thread retainer for supplying a l 58]Field s I 48 254 predetermined thread length of upper thread at theconclusion 252 242/153 of a stitching operation and as a preliminary toa subsequent stitching operation. The retaining arrangement includes athread brake which is released at the end of the stitching [561 ReferCited operation and an eye for drawing the released thread from 21UNITED STATES PATENTS spool or other supply to provide the desiredlength.

1,048,442 12/ l 912 Blair ..1 12/246 10 Claim, 7 Drawing FiguresINVENTOR (ar/ A/ICOL A) marl To ATTORNEY l THREAD RETAINER FOR SEWINGMACHINES FIELD OF THE INVENTION My present invention relates todouble-lockstitch sewing machines, and more particularly, for anarrangement designed to provide a predetermined length of startingthread for the upper thread of the double-lockstitch sewing machinehaving a thread-cutting device.

BACKGROUND OF THE INVENTION In a double-lockstitch sewing machineespecially, and in commercial and industrial sewing machines of varioustypes, a needle is reciprocated through a stitch plate in the table ofthe machine and alternately carries an upper thread from a thread supply(e.g., through the stitch plate and into interlocking engagement with alower thread supplied by a bobbin below the stitch plate.

In a double-lockstitch arrangement with which the system of the presentinvention is particularly desirable, the lower thread is looped aboutthe looped upper thread as the latter is withdrawn through the fabric bythe needle. It is known to provide thread-severing devices in suchmachines and typical among machines of this general type is that of myUS. Pat. No. 3,376,837 issued Apr. 9, 1968. The purpose of thethreadsevering device is, of course, to cut loose the stitched articleand permit the rapid transformation of the machine for the stitching ofanother article.

One of the problems in high-speed commercial and industrial sewingmachines and, in general, sewing machines using upper and lower threads,is that irregularities occur in the commencement of the sewingoperation, especially with fast starts. One of the irregularities ornonuniformities derives from the fact that, even where manual orautomatic devices are provided for severing the upper thread at theconclusion of a prior stitching operation, the length of the upperthread which remains is nonuniform. Should this length be excessivelylong, it remains on the fabric and is unsightly. Should it be too short,the thread may be withdrawn through the eye of the needle andrethreading of the machine will be required. Furthermore, the cuttingdevice does not always position the thread in a reproducible manner andmay, on the one hand, permit the free thread end to overlie the pressorfoot or, on the other hand, cause the free thread end to be clampedbetween the presser foot and the stitch plate. If the thread is clamped,there is little danger that loose stitches will be formed, although anundesirable thread portion may overlie the fabric. However, when thethread merely overlies the presser foot in an undefined manner, a slowmovement of the needle may withdraw the thread from the needle eye asnoted above.

It has already been indicated that the cutting devices for the upper andlower threads may be actuated manually or with the aid of servo devices,the cutting systems being operated as soon as the previously stitchedgoods are drawn along the table to a distance sufficient to provide thesatisfactory length of free end for upper and lower threads. Uponremoval of the previously stitched goods from the machine, the withdrawnlength of the lower thread remains beneath the stitch plate while theupper thread is drawn with the fabric through the stitch hole in thestitch plate.

The withdrawal of the upper thread through thestitch plate to avoid someof the disadvantages mentioned earlier has been proposed, these systemsusing a wiper or swinging member passing beneath the presser foot. Hereagain the position of the thread on the upper side of the stitch plateis well defined and can be either above or below the presser foot andeither lies loosely or is clamped. One of the prior art proposals tolimit the disadvantages of earlier systems has been to use the wiper toplace the thread invariably upon the upper side of the presser foot. Inthis case, the free end of the upper thread is engaged by the gripperfinger during the initial formation of a stitch and is drawn beneath thesurface of the fabric to the underside thereof. This system has thedisadvantage that loose or nonlocked stitches can develop initially,especially for rapid starts ofthe stitching operation. Increasing thelength of the free end is not always a solution since excessively longfree ends are drawn from the needle eye with slow start modes ofstitching.

OBJECTS OF THE INVENTION It is, therefore, the principal object of thepresent invention to provide a thread-retaining system or thread-controlsystem for the upper thread of a sewing machine wherein theaforementioned disadvantages can be avoided.

A more specific object of this invention-is to provide a thread-controlsystem for a double-lockstitch sewing machine provided withthread-severing means for the upper and lower threads, which providesthe desired length of free thread end at the conclusion of a stitchingoperation so that the subsequent stitching operation may commencewithout loose stitches,'l,oss of thread from the needle eye orexcessively long strands atthe ends of a thread seam.

Another object of this invention is to provide, in a sewing machine ofthe character described, a thread-control arrangement which will insureuniform and reproducible starts of a stitchingiseam regardless of therate at which sewing is begun and independently of the degree to whichthe fabric is moved following the prior stitching operation.

SUMMARY OF THE INVENTION These objects and others which will becomeapparent hereinafter are attained, in accordance with my presentinvention by providing a thread brake for the upper thread of the sewingmachine, lever means mounted on the arm thereof, and an actuating systemincluding a member for releasing the thread brake and a second membercooperating with the first member for drawing out the desired length ofthread ofa supply prior to the severing step. The thread brake,according to the present invention, may be of the double-disk type inwhich one disk is spring loaded against another, the thread beingfrictionally engaged between these disks. In this system, the lever forreleasing the thread brake advantageously includes a finger receivablebetween the disks for spreading them apart and relieving pressure uponthe thread.

According to another feature of this invention, the threaddrawing'meansincludes an eye or loop engaging the thread between a pair of fixed eyesfor withdrawing the thread from its normal position linearly spanningthese eyes.

The two levers according to the invention may be coupled with a singleactuator, preferably provided with lost-motion means in order to operatethe thread brake lever first and the loop-forming lever subsequently.Alternatively electromechanic or pneumatic levers may be provided forcontrolling the levers, programming means being employed to operate thelevers in the proper sequence.

According to another feature of this invention, at least one of thelevers is provided with an adjustable fulcrum for regulation of itsstroke and therefore the timing relationship of levers.

DESCRIPTION OF THE DRAWING The above and other objects, features andadvantages of the present invention will become more readily apparentfrom the following description reference being made to the accompanyingdrawing in which:

FIG. 1 is a diagrammatic side elevational view of the arm of adouble-locksn'tch sewing machine according to the invention with thecover plate removed;

FIG. Zis a view similar to FIG. 1 showing the parts of the mechanism ofthe present invention in another position;

FIG. 3- is a detail view of the adjustment means of the system of FIGS.1 and 2 in another position;

FIG. 4 'is a view similar to FIG. 1 or FIG. 2 illustrating anothersystem for actuating the levers of the present invention;

FIG. is a view similar to FIG. 4 showing still another actuating means;

FIG. 6 is a diagrammatic view of the means for operating the controlmember of system of FIGS. 1 and 2; and

FIG. 7 is a detail view of a thread brake which may be used with thesystem of the present invention.

SPECIFIC DESCRIPTION In FIGS. 1 and 2 of the drawing, the arm of thedoublelockstitch sewing machine is represented at l and is provided inthe stitching head of this arm, with a slot 2 in which the thread-feedlever 3 is vertically reciprocable in the usual manner.

To the right of the slot 2, there is provided a fixed threadguide eye 4which is mounted by screws 4a upon a support plate T, carrying themechanism of the present invention. The thread guide 4 has a leg 4bprovided with an aperture 4c through which the thread 7 extends. Belowthe thread-feed lever 3, I provide a double-eye arrangement generallyrepresented at 5 and fixed to the head. The double-eye arrangementcomprises a bracket 5 having an upper eye 5b and a lower eye 50 betweenwhich the loop 17a of a wiper 17 is receivable. The fixed eye 5a of thethread-guide bracket 5 are horizontally staggered so that the thread 7normally forms a thread line in passing through this eye but may bedeflected from the straight line as shown in FIG. 2.

At the upper end of the arm 1, there is provided still another bracket 6provided with thread-guide eyes 6a through which the thread 7 is passedand which serves as a direction-changing device affording some frictionto the path of the thread through the system. The thread 7, of course,derives from a supply spool not illustrated.

From the fixed eyes 6a of the bracket 6, the thread 7 is looped aroundthe thread brake 8 and then passes through the eye 4b, 4c, thethread-feed lever 3 and the eyes 5b and 5a to the needle. The upperthread-cutting arrangement is not seen in FIGS. 1 and 2 but isdiagrammatically represented at 30 in FIG. 6, and may be of anyconventional construction.

The actuating bar 9 (FIGS. 1, 2 and 6) of the actuating means, which maybe connected to the upper thread cutter 30 (for severing the thread) bya lost-motion connection 31 formed by a slot 32 in the bar 9 and a pin33 engageable by the left-hand end of this slot in the extremeright-hand position of the bar 9, is pivotally connected at 34 to abellcrank lever 35 whose fulcrum 36 to the post of the sewing machinearm is located in the region of the stitch-setting mechanism. Thebellcrank lever 35 is coupled with rod 37 at a pivot 38, the rod being,in turn, actuatable by a pedal 39. When the machine operator treads uponthe pedal 39, the bellcrank lever 35 swings in a clockwise sense to drawthe actuating member 9 to the right. A spring representeddiagrammatically at 40 resists this displacement and returns the bar 9into its left-hand position.

The actuating bar 9 is guided along the lateral flank of the arm 1 bymeans not shown and carries a pair of adjustable pins 10 which slide ina slot 11a of a lost-motion arm 11. The slot 11a defines with the pinsan adjustable lost-motion d corresponding to the stroke of the bar 9prior to the displacement of member 11. Member 11 is connected with thethread brake lever 14, the latter being swingable in a fulcrum 14a onthe plate T. The connection is formed by a slot 12 extending generallyvertically in the lever 11 and receiving a pin 13 of the lever 14. Thefoot 14b of lever 14 is generally wedge shaped (FIG. 7) and isreceivable between the disk 8a and 8b of the thread brake to spreadthese disks apart against the spring 8c and permit the thread 7 to bedrawn frictionlessly through this thread brake.

At a fixed location on the arm of the machine, there is provided aneccentric fulcrum 15 which is rotatable as shown in FIGS. 1 and 3 toadjust the actual fulcrum point of the lever 16 (loop-forming lever).The swinging lever 16, in turn, carries a pin 16a which is received inthe lost-motion slot 90 of the bar 9 at its lower end, the swinginglever 16 carries the loop former 17.

The loop-forming wiper 17 is fixed to a setscrew 18 which is bored toreceive the wire from which the member 17 is bent.

In operation, the actuation of the rod 9 by a movement thereof to theright, upon conclusion of a stitching seam, results initially indisplacement of the lever 14 in the counterclockwise sense to spread thedisks of the thread brake 8 and permit the thread 7 to be freely drawnthereto. Shortly thereafter, the further displacement of member 9 swingsthe lever 16 to the right (counterclockwise about the fulcrum 15), todraw its movable eye 17 to the right (FIG. 2) and provide an additionalthread supply between the thread feed lever 3 and the needle. Thelimiting positions of the levers 14 and 16, just prior to thread cutofi,is shown in FIG. 2. A slight additional displacement of member 9suffices to actuate the upper thread cutter 30 (FIG. 6).

In FIG. 4, the lever [14 and the lever 116 each are provided with apneumatic cylinder 114' and 116', the pistons of which are biased intothe opposite or rest positions of the levers by springs diagrammaticallyrepresented at 114" and 116" respectively. A programmer P pneumaticallyactuates the cylinder 114 slightly ahead of the cylinder 116' and thentriggers a pneumatic cylinder coupled with the thread cutter 130 whichis shown diagrammatically. The levers 114 and 116 perform precisely thesame functions as the levers 14 and 16 previously described. Operationof the programmer P can be triggered by a switch or valve controlled bythe operator or by automatic means.

In FIG. 5, the levers 214 and 216 are shown to be displaceable againstthe force of springs 214" and 216" by electromechanical means, i.e.,solenoids 214' and 216' controlled by an electrical programmer P.

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theinvention except as limited by the appended claims.

I claim:

1. A thread-control mechanism for a sewing machine having an armoverhanging a stitch plate, a needle reciprocable on said arm, areciprocable thread-feed member reciprocable on said arm and feed meansfor advancing a sewing thread in succession through said thread-feedmember and said needle, said thread-control mechanism comprising athread brake on said arm forming part of said feed means and engageablewith a sewing thread fed through said thread feed member and needle forretarding passage thereof to said needle, a brake-control leverengageable with said thread brake and swingably mounted on said arm forreleasing the thread, a loop-forming lever swingably mounted on said armand forming part of said feed means for engaging thread between saidthread-feed member and said needle for forming a thread loop, andactuating means forming part of said feed means for sequentiallyoperating said brake-control lever and said loop-forming lever.

2. The mechanism defined in claim 1 wherein said sewing machine has anupper thread cutter for severing said thread, said actuating means beingoperatively connected with said cutter for operating same upon theformation of said loop.

3. The mechanism defined in claim 2, further comprising means foradjusting the stroke of at least one of said levers.

4. The mechanism defined in claim 2, further comprising spring meansyieldably resistant to displacement of at least one of said levers bysaid actuating means.

5. The mechanism defined in claim 4 wherein said means includes at leastone pneumatic cylinder.

6. The mechanism defined in claim 4 wherein said actuating meansincludes at least one electromagnet.

7. The mechanism defined in claim 4 wherein said actuating meansincludes a bar mounted in said arm and shiftable longitudinally thereofand lost-motion means connecting said bar with said loop-forming lever.

l actuating lever being provided with a movable eye received betweensaid fixed arms.

10. The mechanism defined in claim 9, wherein said thread brake has aspring-biased disk, said brake-control lever engaging said disk.

I0! l 1F

1. A thread-control mechanism for a sewing machine having an armoverhanging a stitch plate, a needle reciprocable on said arm, areciprocable thread-feed member reciprocable on said arm and feed meansfor advancing a sewing thread in succession through said thread-feedmember and said needle, said thread-control mechanism comprising athread brake on said arm forming part of said feed means and engageablewith a sewing thread fed through said thread feed member and needle forretarding passage thereof to said needle, a brake-control leverengageable with said thread brake and swingably mounted on said arm forreleasing the thread, a loop-forming lever swingably mounted on said armand forming part of said feed means for engaging thread beTween saidthread-feed member and said needle for forming a thread loop, andactuating means forming part of said feed means for sequentiallyoperating said brake-control lever and said loop-forming lever.
 2. Themechanism defined in claim 1 wherein said sewing machine has an upperthread cutter for severing said thread, said actuating means beingoperatively connected with said cutter for operating same upon theformation of said loop.
 3. The mechanism defined in claim 2, furthercomprising means for adjusting the stroke of at least one of saidlevers.
 4. The mechanism defined in claim 2, further comprising springmeans yieldably resistant to displacement of at least one of said leversby said actuating means.
 5. The mechanism defined in claim 4 whereinsaid actuating means includes at least one pneumatic cylinder.
 6. Themechanism defined in claim 4 wherein said actuating means includes atleast one electromagnet.
 7. The mechanism defined in claim 4 whereinsaid actuating means includes a bar mounted in said arm and shiftablelongitudinally thereof and lost-motion means connecting said bar withsaid loop-forming lever.
 8. The mechanism defined in claim 7 whereinsaid loop-forming lever is provided with an eccentric fulcrum rotatableto shift the fulcrum axis on said arm.
 9. The mechanism defined in claim8, further comprising a pair of vertically spaced fixed thread-guidingeyes between said thread-feed member and said needle, said loop-forminglever being provided with a movable eye received between said fixedarms.
 10. The mechanism defined in claim 9, wherein said thread brakehas a spring-biased disk, said brake-control lever engaging said disk.